The Linear density, linear mass density or linear mass is a measure of mass per unit of length, and it is a characteristic of strings or other one-dimensional objects.
Applicable units are those of quantitykind:LinearDensity
http://en.wikipedia.org/wiki/Linear_density
The Linear density, linear mass density or linear mass is a measure of mass per unit of length, and it is a characteristic of strings or other one-dimensional objects.
$\rho_l = \frac{dm}{dl}$, where $m$ is mass and $l$ is length.
http://www.iso.org/iso/catalogue_detail?csnumber=31889